1. Field of the Invention
The present invention relates to a normalizing circuit used in a digital processor in which binary data is manipulated, and more particularly to a normalizing circuit used in an arithmetic computing apparatus to execute a binary floating point operation.
2. Description of the Prior Art
A digital processor manipulates a bit string consisting of a group of binary data "zeros" and "ones". Particularly, in an arithmetic operation, a bit shift operation of the bit string is usually required. The bit shift operation typically is used in a floating point arithmetic operation to raise the precision of the arithmetic operation and is executed by a normalizing circuit having a bit shifter (e.g. a shift register). The normalizing circuit is used to take off "zeros" from the upper bit portion of a mantissa. That is, in floating point operation, a binary data "one" must be positioned at a leading bit (MSB) of the mantissa. The bit shifter used in the normalizing circuit shifts a bit string of the mantissa leftwardly such that a leading "one" of the mantissa is positioned at a most left-hand side bit. This shift operation has been executed by software in the prior art. Namely, a bit string of a mantissa is shifted leftward one bit by one bit according to a shift clock and is checked whether the left-most bit is "one" or "zero" in every bit shift operation. Therefore, a very long period is required until a leading "one" of the mantissa is positioned at the left most side. The drawback of this technique is most significant when a long bit string is computed. Since a long bit string (e.g. eighty bits/a word), in general, is used in a highpower floating point processor, a very long time must elapse before a normalizing operation can be completed. Therefore, minimizing the normalizing operation is most important in obtaining high speed processing. Further, the normalizing operation containing a bit shift operation is required not only in the floating point processor but also in many other digital processors such as an image processor, a sound processor and the like.